Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.90	3.526%	$116.8809	$116.88	$116.90	$116.90
Purchase #2	$180.39	8.545%	$195.8043	$195.80	$195.80	$195.80
Purchase #3	$85.98	11.561%	$95.9201	$95.92	$95.90	$95.90
Purchase #4	$157.28	6.330%	$167.2358	$167.24	$167.25	$167.20
Purchase #5	$204.40	4.484%	$213.5653	$213.57	$213.55	$213.60
Purchase #6	$54.89	11.799%	$61.3665	$61.37	$61.35	$61.40
Purchase #7	$123.38	6.507%	$131.4083	$131.41	$131.40	$131.40
7 purchase totals =	$919.22		$982.1812	$982.19	$982.15	$982.20